1. It's a very simple recipe.

Question

2. Spaghetti is a very simple recipe.
3. To make speghetti is a very simple recipe.
4. How to make spghetti is a very simple recipe.
5. ______ is a very simple recipe.
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Which one is grammatical? Which terms can be put in the blank in #5?
Is 'It' in #1 a "situation it" which doesn't refer to a specific one? Or can 'it' refer to 'spaghetti' or other things?

Answer 1

They're all grammatical. "It" refers to a specific recipe and would be understood to mean something, like spaghetti, already mentioned earlier.